Typically in the valve art, a reduction in the pressure of the fluid passing through the valve results in a corresponding increase in the velocity of the fluid. If the pressure reduction is substantial enough, the velocity of the fluid will approach sonic levels which results in excessive vibration and valve noise, both of which will hasten the deterioration of the valve. In addition, if the pressure of the fluid drops below its vaporization pressure, partial vaporization of the fluid may occur resulting in a process called cavitation which greatly accelerates the deterioration of the valve. These problems have been partially alleviated by drag valves which utilize multi-turn passageways to create a pressure drop while keeping fluid velocity nearly constant. However, these valves have no provisions for varying the number of multi-turn passageways to which the fluid passing therethrough is subjected. Thus, the pressure drop, i.e., the fluidic impedance, of these valves is preset and cannot be varied to compensate for various fluids which may pass through the valve. This drag valve concept has been applied to ball valves as may be seen in U.S. Pat. No. 4,085,774 which teaches a ball valve utilizing a plurality of contractions and expansions in the fluid passageways to produce a pressure drop. However, there is no teaching of accomplishing a pressure drop by a multi-turn labyrinth nor is there any teaching with respect to varying the pressure drop by varying the multi-turn labyrinth.